From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: qdisk vs. file as vbd type Date: Fri, 10 Jan 2014 16:00:00 +0100 Message-ID: <20140110150000.GA20287@aepfle.de> References: <20140110144024.GA19611@aepfle.de> <1389365236.19142.54.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1389365236.19142.54.camel@kazak.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Li Dongyang , Konrad Rzeszutek Wilk Cc: Ian Campbell , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Fri, Jan 10, Ian Campbell wrote: > On Fri, 2014-01-10 at 15:40 +0100, Olaf Hering wrote: > > What is the reason the backend 'type' property of a configured disk is > > now "qdisk" instead of "file"? > > Because qdisk is the backend instead of loop+blk (==file) I think this > just happens naturally. > > > Would the guest really care about that > > detail? For example block-front currently just checks for "phy" and > > "file" when deciding if discard should be enabled. > > That sounds entirely bogus, it should be checking for some sort of > feature-discard. It does that, then calls blkfront_setup_discard which in turn knows just about phy and file. And I wonder why it does that. Maybe this function should be simplified to assume that if its called feature_discard can be enabled. And if both discard-granularity/discard-alignment exist those properties should be assigned, similar for discard-secure. Now that I look at the history of blkfront_setup_discard: Li, Konrad, why does that function care at all about the 'type'? Shouldnt that check be removed? Olaf